/*
 * Alloy Analyzer 4 -- Copyright (c) 2006-2008, Felix Chang
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package edu.mit.csail.sdg.alloy4viz;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import edu.mit.csail.sdg.alloy4.Util;

/**
 * Immutable; represents an Alloy relation of 2 or higher arity.
 *
 * <p><b>Thread Safety:</b> Can be called only by the AWT event thread.
 */

public final class AlloyRelation extends AlloyElement {

    /** This caches an instance of the "extends" AlloyRelation, so we don't have to keep re-constructing it. */
    public static final AlloyRelation EXTENDS = new AlloyRelation("extends", false, false, Util.asList(AlloyType.UNIV, AlloyType.UNIV));

    /** This caches an instance of the "in" AlloyRelation, so we don't have to keep re-constructing it. */
    public static final AlloyRelation IN = new AlloyRelation("in", false, false, Util.asList(AlloyType.SET, AlloyType.UNIV));

    /** The unmodifiable list of types. */
    private final List<AlloyType> types;

    /** Records whether this relation is known to be "private"; NOTE: this value is NOT USED during equals() comparison. */
    public final boolean isPrivate;

    /** Records whether this relation is known to be "meta"; NOTE: this value is NOT USED during equals() comparison. */
    public final boolean isMeta;

    /** Constructs a new AlloyRelation with that name and that list of types; types.size() must be 2 or above. */
    public AlloyRelation(String name, boolean isPrivate, boolean isMeta, List<AlloyType> types) {
        super(name);
        if (types==null || types.size()<2)
            throw new RuntimeException("An AlloyRelation object must have 2 or more types.");
        this.types = Collections.unmodifiableList(new ArrayList<AlloyType>(types));
        this.isPrivate = isPrivate;
        this.isMeta = isMeta;
    }

    /**
     * Project this relation and return an unmodifiable list of remaining types (after removing zero or more columns)
     * @param columns - the collection of columns to remove (0 is the first column, 1 is the second column...)
     */
    public List<AlloyType> project(Collection<Integer> columns) {
        List<AlloyType> list=new ArrayList<AlloyType>(types.size());
        for(int i=0; i<types.size(); i++) if (!columns.contains(i)) list.add(types.get(i));
        if (list.size()==types.size()) return this.types; else return Collections.unmodifiableList(list);
    }

    /** Returns an unmodifiable list of AlloyTypes representing the relation's type. */
    public List<AlloyType> getTypes() { return types; }

    /** Returns the arity of the relation. */
    public int getArity() { return types.size(); }

    /**
     * When comparing two AlloyRelation objects, we first compare the name, then the arity, then the types.
     * <br> We guarantee x.equals(y) iff x.compareTo(y)==0
     */
    public int compareTo(AlloyRelation other) {
        if (other==null) return 1;
        // First compare the names.
        int n=Util.slashComparator.compare(getName(), other.getName()); if (n!=0) return n;
        // Now compare the arity of the two relations
        int arity = types.size();
        if (arity!=other.types.size()) return (arity<other.types.size())?-1:1;
        // Finally, compare each AlloyType
        for(int i=0; i<arity; i++) {
            n=types.get(i).compareTo(other.types.get(i));
            if (n!=0) return n;
        }
        return 0;
    }

    /**
     * When comparing two AlloyRelation objects, we first compare the name, then the arity, then the types.
     * <br> We guarantee x.equals(y) iff x.compareTo(y)==0
     */
    public int compareTo(AlloyElement other) {
        if (!(other instanceof AlloyRelation)) return 1;
        return compareTo((AlloyRelation)other);
    }

    /** This value is used to display this type in the Visualizer's customization screen. */
    @Override public String toString() {
        String answer="<html>";
        boolean first=true;
        for(AlloyType type: getTypes()) {
            if (first) {first=false; answer=answer+getName()+" :  ";} else answer=answer+" -&gt; ";
            answer=answer+type.getName();
        }
        return answer+"</html>";
    }

    /** Two relations are equal if they have the same name, and the same list of types. */
    @Override public boolean equals(Object other) {
        if (!(other instanceof AlloyRelation)) return false;
        if (other==this) return true;
        AlloyRelation otherRelation = (AlloyRelation)other;
        return getName().equals(otherRelation.getName()) && types.equals(otherRelation.types);
    }

    /** Computes a hash code based on the name and the list of types. */
    @Override public int hashCode() { return 5*getName().hashCode() + 7*types.hashCode(); }
}
